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| United States Patent |
6,036,830
|
|
Gancet
, et al.
|
March 14, 2000
|
Desalination of aqueous sulphonamide solutions
Abstract
In order to remove the salts (in particular NH.sub.4 Cl) present in an
aqueous sulphonamide solution (in particular CH.sub.3 SO.sub.2 NH.sub.2),
the solution is subjected to a two-compartment electrodialysis. By
maintaining the pH at a value below 7, the formation of ammonia is
avoided. The demineralized solution can be concentrated in order to
receover after crystallization, the sulphonamide.
| Inventors:
|
Gancet; Christian (Lons, FR);
Lauranson; Didier (Lons, FR);
Perie; Frederic (Billere, FR)
|
| Assignee:
|
Elf Atochem S.A. (FR)
|
| Appl. No.:
|
172172 |
| Filed:
|
October 14, 1998 |
Foreign Application Priority Data
| Current U.S. Class: |
204/529; 204/530; 204/541 |
| Intern'l Class: |
B01D 061/44 |
| Field of Search: |
204/529,530,541
|
References Cited
U.S. Patent Documents
| 5145569 | Sep., 1992 | Schneider et al. | 204/529.
|
| 5282939 | Feb., 1994 | Voss | 204/529.
|
| 5597466 | Jan., 1997 | Bauer et al. | 204/529.
|
| Foreign Patent Documents |
| 536021 | Apr., 1993 | EP.
| |
| 360093 | Apr., 1993 | EP.
| |
| 2708266 | Feb., 1995 | FR.
| |
| 63-083058 | Apr., 1988 | JP.
| |
| 7-080254 | Mar., 1995 | JP.
| |
Other References
French Search Report dated Jul. 6, 1998.
|
Primary Examiner: Phasge; Arwn S.
Claims
We claim:
1. Process for desalination an aqueous sulphonamide solution, comprising
subjecting this solution, maintained in an acidic pH, to a two-compartment
electrodialysis.
2. Process according to claim 1, wherein the pH is maintained between 2 and
6.
3. Process according to claim 2, wherein the pH is between 3 and 5.
4. Process according to claim 1, wherein the acidic pH is maintained by
addition of hydrochloric acid to the saline solution.
5. Process according to claim 1, wherein the sulphonamide concentration of
the solution to be desalinated is between 0.1 M and its solubility limit
in the saline solution.
6. Process according to claim 5, wherein the sulphonamide concentration is
between 0.5 and 2 M.
7. Process according to claim 1, wherein the sulphonamide is
methanesulphonamide.
Description
FIELD OF THE INVENTION
The present invention concerns the field of water-soluble sulphonamides and
relates more particularly to a process for allowing the recovery and
purification of sulphonamides obtained by an aqueous-phase synthetic
process. The invention relates more especially to methanesulphonamide
CH.sub.3 SO.sub.2 NH.sub.2 (also referred to as MSAM), but more generally
to all water-soluble sulphonamides.
BACKGROUND OF THE INVENTION
When sulphonamides are prepared in aqueous phase, an aqueous sulphonamide
solution is finally obtained, which, in order to be able to isolate the
sulphonamide, must be concentrated so as to crystallize the sulphonamide.
Unfortunately, the aqueous solution to be concentrated generally contains
salts, in particular ammonium chloride, which makes this concentration
step difficult.
The prior art does not mention the use of membrane techniques in processes
for the synthesis of sulphonamides, which, such as that of patent FR
2,708,266, use reactions carried out in a solvent medium such as
acetonitrile or propionitrile.
The use of electrodialysis membranes to desalinate aqueous solutions is
known to those skilled in the art and forms the subject, in particular, of
patent EP 536,021, which relates to the desalination of aqueous solutions
of polar aprotic solvents.
Application of this technique to the desalination of aqueous sulphonamide
solutions derived from an aqueous-phase synthetic process is, however,
unknown. Given that the sulphonamides concerned (in particular MSAM) have
a relatively low molecular mass, they are liable to diffuse considerably
across the membranes and it might be feared that high desalination yields
could not be obtained.
DESCRIPTION OF THE INVENTION
It has now been found that the salts present in an aqueous sulphonamide
solution can be removed with a high desalination yield by subjecting this
solution to a two-compartment electrodialysis, provided that the solution
is maintained at an acidic pH.
The salts (in particular NH.sub.4 Cl) pass from the solution (diluate)
containing the sulphonamide to a receiver solution (concentrate) and,
provided that the system remains at an acidic pH in order to avoid the
diffusion of non-protonated ammonia, the removal of NH.sub.4 Cl poses no
problems.
The subject of the invention is thus a process for desalinating an aqueous
sulphonamide solution, characterized in that this solution, maintained at
an acidic pH, is subjected to a two-compartment electrodialysis.
In order to carry out the process according to the invention, commercial
cationic and anionic ion-exchange membranes can be used, such as, for
example, those sold by the company Asahi Glass under the name
Selemion.RTM., by the company Tokuyama Soda under the name Neosepta.RTM.
or by the company Aqualytics. These commercial membranes generally have a
thickness of between 0.1 and 1 mm and a pore diameter of between 1 and 30
.mu.m. The ion-exchange membranes usually consist of a polymer matrix (for
example polystyrene/divinylbenzene) onto which anionic groups (for example
carboxylate or sulphonate) are chemically bonded for the cation-exchange
resins, or cationic groups (for example substituted ammonium) for the
anion-exchange resins. So-called "selective" membranes, with a narrower
polymer structure, have been developed in order to retain di- and
trivalent ions (sulphate, calcium, magnesium, etc.) and to allow
monovalent ions (chloride, sodium, etc.) to pass through.
The sulphonamide concentration of the solution to be desalinated can vary
within a wide range and is generally between 0.1 M and the solubility
limit of the sulphonamide considered. This concentration is preferably
between 0.5 and 2 M.
In accordance with the process according to the invention, the solution to
be desalinated is maintained at an acidic pH, preferably between 2 and 6
and more particularly between 3 and 5. This can be done, for example, by
addition of dilute HCl (0.05 to 0.5 M) to the saline solution. HCl is
usually suitable, but depending on the anion of the salt to be removed,
other monoacids can be used.
EXAMPLES
The examples which follow illustrate the invention without limiting it.
EXAMPLE 1
The solution to be treated was an equimolar mixture of methanesulphonamide
(MSAM) and NH.sub.4 Cl at pH 4.4. The receiver solution was a 5 g/l sodium
chloride solution, as well as the electrolyte solution.
An SRTI electrodialyser of type P1 equipped with AMV and CMV standard
membranes from Asahi Glass for a cell surface of 0.138 m.sup.2 (for a
two-compartment device, 1 m.sup.2 of cell corresponds to 1 m.sup.2 of
cationic membrane+1 m.sup.2 of anionic membrane, i.e. 2 m.sup.2 of
membranes) was used.
The current density applied was 435 A/m.sup.2, except at the end of the
test when the conductivity was too low; a voltage of 1.5 V per cell was
then applied.
During the electrodialysis, the pH was maintained between 3 and 5 by
addition of 0.1 M HCl so as to avoid any formation of ammonia which might
diffuse and contaminate the MSAM produced.
The MSAM was analysed by gas chromatography. The ammonium chloride was
monitored by conductimetry during the test and measured by ionic
chromatography on samples taken.
The duration of the test was 0.66 hour. The roductivity of the device was
11.3 kg of 1 M MSAM solution treated per hour and per m.sup.2, the energy
consumed being 45.1 kWh per tonne of 1 M MSAM solution treated.
Table 1 below indicates the level of demineralization achieved on the MSAM
solution after the electrodialysis treatment.
TABLE 1
______________________________________
CONCENTRATION (millimol/liters)
initial final
______________________________________
MSAM 1000 880
NH.sub.4 Cl
1000 2.9
______________________________________
Table 2 below indicates the salt and MSAM concentrations during the test,
as well as the mass balance for the MSAM.
TABLE 2
______________________________________
MSAM compartment
Salt compartment
(diluate) (concentrate)
______________________________________
NH.sub.4 Cl
concentration
(millimol/liter)
initial 1000 85.5
final 2.9 1070
MSAM
concentration
(millimol/liter)
initial 1000 0
final 880 55
Mass balance for
MSAM (in g)
initial mass 94 0
final mass 83.5 7.7
______________________________________
These results indicate that MSAM is correctly retained in the diluate
compartment, the losses by passive diffusion being about 8.4% by weight.
The yield observed is 91.6% by weight.
Depending on the target level of yield of MSAM, the final salt
concentration can be adjusted by stopping the electrodialysis before
depletion of the saline solution.
The final NH.sub.4 Cl concentration is limited by the minimum conductivity
to be conserved in order to allow the passage of current. In order to
obtain more thorough levels of demineralization, the low conductivity of
the solution can be compensated for by placing a resin or an ion-exchange
felt pad in the salt compartment of the electrodialyser.
EXAMPLE 2
In order to treat an equimolar mixture of MSAM and NH.sub.4 Cl at pH 4.15,
the process was performed as in Example 1, but using ASV and CHV selective
membranes from Asahi Glass.
The duration of the test was 0.7 hour. The productivity of the device was
10.1 kg of 1 M MSAM solution treated per hour and per m.sup.2, the energy
consumed being 45.8 kWh per tonne of 1 M MSAM solution treated.
Table 3 below indicates the level of demineralization achieved on the MSAM
solution after the electrodialysis treatment.
TABLE 3
______________________________________
CONCENTRATION (millmol/liters)
initial final
______________________________________
MSAM 1000 845
NH.sub.4 Cl 1000 0.6
______________________________________
Table 4 below indicates the salt and MSAM concentrations during the test,
as well as the mass balance for MSAM.
TABLE 4
______________________________________
MSAM compartment
Salt compartment
(diluate) (concentrate)
______________________________________
NH.sub.4 Cl
concentration
(millimol/liter)
initial 1000 93.5
final 0.6 835
MSAM
concentration
(millimol/liter)
initial 1000 0
final 845 22
Mass balance for
MSAM (in g)
initial mass 92.5 0
final mass 75.2 2.6
______________________________________
MSAM is correctly retained in the diluate compartment, the losses by
passive diffusion being about 3.3% by weight. The yield observed is thus
96.7% by weight.
This example shows that the use of more selective membranes (with a
narrower polymer structure) allows the level of loss of MSAM to be reduced
from 8.4 to 3.3%.
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